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https://issues.apache.org/jira/browse/HDFS-3107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14277534#comment-14277534
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Colin Patrick McCabe commented on HDFS-3107:
--------------------------------------------
I can't speak for anyone else on this thread, but I personally think we should
give it a week or two and then merge to branch-2. I hope anyone with
unresolved concerns will post follow-ups by then.
In the future we should probably do this kind of work in a branch. It would
have sped up the work, because we could have committed things quickly to the
branch. git has made branches easier than ever. The requirement to get three
+1s in a branch might seem onerous, but a feature of this size needs several
eyes on it anyway, so the review requirement ended up being about the same (or
even more).
> HDFS truncate
> -------------
>
> Key: HDFS-3107
> URL: https://issues.apache.org/jira/browse/HDFS-3107
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: datanode, namenode
> Reporter: Lei Chang
> Assignee: Plamen Jeliazkov
> Fix For: 3.0.0
>
> Attachments: HDFS-3107-13.patch, HDFS-3107-14.patch,
> HDFS-3107-15.patch, HDFS-3107-HDFS-7056-combined.patch, HDFS-3107.008.patch,
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch,
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch,
> HDFS-3107.patch, HDFS-3107.patch, HDFS-3107.patch, HDFS_truncate.pdf,
> HDFS_truncate.pdf, HDFS_truncate.pdf, HDFS_truncate_semantics_Mar15.pdf,
> HDFS_truncate_semantics_Mar21.pdf, editsStored, editsStored.xml
>
> Original Estimate: 1,344h
> Remaining Estimate: 1,344h
>
> Systems with transaction support often need to undo changes made to the
> underlying storage when a transaction is aborted. Currently HDFS does not
> support truncate (a standard Posix operation) which is a reverse operation of
> append, which makes upper layer applications use ugly workarounds (such as
> keeping track of the discarded byte range per file in a separate metadata
> store, and periodically running a vacuum process to rewrite compacted files)
> to overcome this limitation of HDFS.
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